56 research outputs found
Synthesis and Crystal Structure of a Copper(II) Benzoate Complex Bearing a Bis-2,2âČ-Tetrahydrofuryl Peroxide Moiety
Complex [Cu2(ben)4·2THFâ(η1âO2)]â (2) (ben=C6H5CO2â benzoate; THF=tetrahydrofuran) was isolated when a solution of Cu2(ben)4·2THF (1) in THF upon natural sunlight irradiation yields crystals suitable for single-crystal X-ray diffraction analysis. 2, crystallized in the C2/c monoclinic space group, Z=8, V=3394.2 (4) Ă
3, and the unit cell parameters a=9.7935(7) Ă
, b=19.0055 (13) Ă
, c=18.2997 (13) Ă
, α=90°, ÎČ=94.7996 (11)Âș and Îł=90°. This is the first example of a polymeric copper(II) carboxylate compound stabilizing a peroxo group via its apical ligand (THF molecule). Additionally, 2 was also characterized by elemental analysis, Fourier-transformed infrared spectroscopy (FTIR) and Raman spectroscopyUniversidad de Costa Rica/[804-B7-279]/UCR/Costa RicaUniversidad de Costa Rica/[804-B0-650]/UCR/Costa RicaUCR::VicerrectorĂa de Docencia::Ciencias BĂĄsicas::Facultad de Ciencias::Escuela de QuĂmicaUCR::VicerrectorĂa de InvestigaciĂłn::Unidades de InvestigaciĂłn::Ciencias BĂĄsicas::Centro de InvestigaciĂłn en ElectroquĂmica y EnergĂa QuĂmica (CELEQ
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Article discussing research on L- and M-shell x-ray production cross sections of Nd, Gd, Ho, Yb, Au, and Pb by 25-MeV carbon and 32-MeV oxygen ions
International Consensus Statement on Rhinology and Allergy: Rhinosinusitis
Background: The 5 years since the publication of the first International Consensus Statement on Allergy and Rhinology: Rhinosinusitis (ICARâRS) has witnessed foundational progress in our understanding and treatment of rhinologic disease. These advances are reflected within the more than 40 new topics covered within the ICARâRSâ2021 as well as updates to the original 140 topics. This executive summary consolidates the evidenceâbased findings of the document. Methods: ICARâRS presents over 180 topics in the forms of evidenceâbased reviews with recommendations (EBRRs), evidenceâbased reviews, and literature reviews. The highest grade structured recommendations of the EBRR sections are summarized in this executive summary. Results: ICARâRSâ2021 covers 22 topics regarding the medical management of RS, which are grade A/B and are presented in the executive summary. Additionally, 4 topics regarding the surgical management of RS are grade A/B and are presented in the executive summary. Finally, a comprehensive evidenceâbased management algorithm is provided. Conclusion: This ICARâRSâ2021 executive summary provides a compilation of the evidenceâbased recommendations for medical and surgical treatment of the most common forms of RS
Validation of experimental charge-density refinement strategies: when do we overfit?
A cross-validation method is supplied to judge between various strategies in multipole refinement procedures. Its application enables straightforward detection of whether the refinement of additional parameters leads to an improvement in the model or an overfitting of the given data. For all tested data sets it was possible to prove that the multipole parameters of atoms in comparable chemical environments should be constrained to be identical. In an automated approach, this method additionally delivers parameter distributions of k different refinements. These distributions can be used for further error diagnostics, e.g. to detect erroneously defined parameters or incorrectly determined reflections. Visualization tools show the variation in the parameters. These different refinements also provide rough estimates for the standard deviation of topological parameters
Mixed valence η6-arene cobalt(i) and cobalt(ii) compound
Azhakar R, Ghadwal R, Roesky HW, Hey J, Krause L, Stalke D. Mixed valence η6-arene cobalt(i) and cobalt(ii) compound. Dalton Transactions. 2013;42(28): 10277.The first carbonyl free mixed valence cobalt(I)/cobalt(II) compound [2{L2Co(I)(η6-C7H8)}]2+ [Co(II)2Cl6]2â (1) [L = PhC(NtBu)2SiCl] was obtained by the reaction of four equivalents of anhydrous CoCl2 with five equivalents of N-heterocyclic chlorosilylene L. In contrast, the reaction of L with CoBr2 yielded [L2CoBr2] (2). Compound 1 was formed by the cleavage of CoâCl bonds, the reduction of Co(II) to Co(I) and by the coordination of a toluene molecule. The chlorosilylene (L) functions as a reducing agent as well as a neutral Ï-donor ligand. The toluene molecule coordinates to the Co(I) atom in an η6-fashion
Triggered Exchange of Anionic for Neutral Guests inside a Cationic Coordination Cage
Molecular encapsulation processes
under the control of an external
trigger play a major role in biological signal transduction processes
and enzyme catalysis. Here, we present an artificial mimic of a controllable
host system that forms via self-assembly from a simple bis-monodentate
ligand and PdÂ(II) cations. The resulting interpenetrated double cage
features three consecutive pockets which initially contain one tetrafluoroborate
anion, each. Activation of this host system with two halide anions
triggers a conformational change that renders the central pocket susceptible
to the uptake of small neutral guest molecules. Thereby, the pentacationic
cage expels the central anion and replaces it with a neutral molecule
to give a hexacationic species. The cage structures prior and after
the halide triggered binding of benzene were examined by X-ray crystallography,
ESI MS, and NMR techniques. The kinetics and thermodynamics of the
encapsulation of benzene, cyclohexane, and norbornadiene are compared
Triggered Exchange of Anionic for Neutral Guests inside a Cationic Coordination Cage
Molecular encapsulation processes
under the control of an external
trigger play a major role in biological signal transduction processes
and enzyme catalysis. Here, we present an artificial mimic of a controllable
host system that forms via self-assembly from a simple bis-monodentate
ligand and PdÂ(II) cations. The resulting interpenetrated double cage
features three consecutive pockets which initially contain one tetrafluoroborate
anion, each. Activation of this host system with two halide anions
triggers a conformational change that renders the central pocket susceptible
to the uptake of small neutral guest molecules. Thereby, the pentacationic
cage expels the central anion and replaces it with a neutral molecule
to give a hexacationic species. The cage structures prior and after
the halide triggered binding of benzene were examined by X-ray crystallography,
ESI MS, and NMR techniques. The kinetics and thermodynamics of the
encapsulation of benzene, cyclohexane, and norbornadiene are compared
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